Method of manufacturing disposable cold pack and related disposable cold pack containing phosphate ammonium nitrate

ABSTRACT

Plastic sheet can be heat-sealed to form a water-tight envelope having an open top. A water-tight frangible container can be loaded into the envelope through the open top. The water-tight frangible container can contain a predetermined amount of water. A predetermined amount of phosphate ammonium nitrate (PAN) can be loaded into the envelope through the open top. The relative proportion of the predetermined amounts of phosphate ammonium nitrate to water can be selected to provide a target cooling effect to a portion of a body to which cooling is to be applied. The open top of the envelope can be heat-sealed to form a water-tight outer pack.

FIELD

The present invention relates to cold packs.

BACKGROUND

Reusable cold packs are known, however, these are not used in manyclinical situations because they require freezing and because ofsterility concerns and the need to reduce the spread of disease.

Certain kinds of disposable cold packs are also known, however, thesesuffer from drawbacks including poor manufacturability, designcomplexity, and high unit cost.

In addition, certain materials used in disposable cold packs, such aspure ammonium nitrate, may be controlled or regulated and thereforedifficult to obtain and potentially hazardous to store in quantitiessuitable for mass production of disposable cold packs. Pure ammoniumnitrate can be highly reactive and susceptible to combustion orexplosion.

Therefore, the prior art suffers for lack of a disposable cold pack thatis readily manufacturable in large quantities and convenient and safe touse in various clinical situations.

SUMMARY

The present invention relates to disposable cold packs for cold therapyand methods of manufacturing same. Such disposable cold packs caninclude an amount of phosphate ammonium nitrate (PAN).

According to one aspect of the present invention, a method ofmanufacturing a disposable cold pack for cold therapy includesheat-sealing plastic sheet to form a water-tight envelope having an opentop, loading a predetermined amount of phosphate ammonium nitrate intothe envelope through the open top, and loading a water-tight frangiblecontainer into the envelope through the open top, the water-tightfrangible container containing a predetermined amount of water. Arelative proportion of the predetermined amount of phosphate ammoniumnitrate to the predetermined amount of water is selected to provide atarget cooling effect to a portion of a body to which cooling isapplied. The method further includes heat-sealing the open top of theenvelope to form a water-tight outer pack.

According to another aspect of the present invention, a disposable coldpack for providing cold therapy to a portion of a body includes an outerpack formed of a water-tight sealed envelope, an amount of phosphateammonium nitrate contained inside the outer pack, and a water-tightfrangible container disposed inside the outer pack. The outer pack hasan outer surface configured for placement on skin or clothing coveringthe portion of the body. The water-tight frangible container containswater. The water-tight frangible container is configured to release thewater into the inside of the outer pack in response to an external forceapplied to the outer pack. A relative proportion of the phosphateammonium nitrate to the water is selected to provide a target coolingeffect to the portion of the body.

According to another aspect of the present invention, a disposable coldpack for providing cold therapy to a portion of a body includes an outerpack formed of a water-tight sealed envelope formed of at least onelayer of plastic sheet that is heat-sealed at one or more heat-sealedseams, an amount of phosphate ammonium nitrate contained inside theouter pack, and a water-tight frangible container disposed inside theouter pack. The plastic sheet has a fibre texture at an outer surface ofthe outer pack to configure the outer pack for placement in directcontact with skin of the portion of the body. The water-tight frangiblecontainer includes a heat-sealed plastic bag containing water. Thewater-tight frangible container is configured to rupture and release thewater into the inside of the outer pack in response to an external forceapplied to the outer pack. A relative proportion of the phosphateammonium nitrate to the water is selected to provide a target coolingeffect to the portion of the body. The relative proportion is about 50%phosphate ammonium nitrate and about 50% water, by weight.

BRIEF DESCRIPTION OF THE FIGURES

The drawings illustrate, by way of example only, embodiments of thepresent invention.

FIG. 1 is a perspective view of a cold pack according to an embodimentof the present invention.

FIG. 2 is a cross-sectional view of the cold pack of FIG. 1.

FIG. 3 is a perspective view of a cold pack with a strap according toanother embodiment of the present invention.

FIG. 4 is a flowchart of a method of manufacturing a disposable coldpack according to an embodiment of the present invention.

FIG. 5 is a close-up view of the attachment of the strap to the coldpack of FIG. 3.

FIG. 6 is a diagram of stock side-sealed material that can be cut tolength to form envelopes of various lengths.

FIG. 7 is a diagram of another embodiment of a cold pack having a strapconnected to an end opposite of the end that is used for filling thecold pack.

FIG. 8 is a diagram of a cold pack shaped and sized to fit a femaleperineum according to another embodiment of the present invention.

DETAILED DESCRIPTION

FIG. 1 shows a disposable cold pack 10 for providing cold therapy. Thecold pack 10 can be applied to a portion of a person's body, such as anarm, leg, neck, abdomen, etc. Cold pack 10 contains materials to producean endothermic reaction, such as phosphate ammonium nitrate. Phosphateammonium nitrate (also referred to as “ammonium phosphate nitrate” orPAN) is typically used as a source of elemental nitrogen in fertilizers.However, cold pack 10 contains an amount of phosphate ammonium nitratewhich reacts spontaneously and endothermically with water, so as to coolthe portion of the body for therapeutic effect. The cold pack 10 may beused to reduce swelling or discomfort associated with injury, and mayfind other uses as well. The cold pack 10 is disposable, in that oncethe endothermic reaction is complete, the cold pack 10 is not reusableand can be discarded. The cold pack 10 may be referred to as an instantcold pack because the mixture is selected so that the endothermicreaction occurs quickly. Using phosphate ammonium nitrate provides thebenefit of temperatures comparable to those that can be attained whenusing ammonium nitrate alone, but without the need to use ammoniumnitrate and be limited by its distinct disadvantages. For example,ammonium nitrate alone can be highly reactive and susceptible tocombustion or explosion, and is therefore usually heavily regulated orcontrolled. In contrast, phosphate ammonium nitrate is typically notflammable.

The cold pack 10 includes an outer pack 12 formed of a water-tightsealed envelope 14. The envelope 14 may be formed of at least one layerof plastic sheet, which can be heat-sealed at one or more seams 16 thatdefine the outer perimeter of the envelope 14. In the embodimentdepicted, all four edges of the rectangular envelope 14 have heat-sealedseams 16. In other embodiments, three edges of the rectangular envelope14 have heat-sealed seams 16, with the fourth edge being formed by afold of a single sheet of plastic.

The plastic sheet may be of any suitable polymer, such as polyethylene,polyester, polypropylene, nylon, polyvinyl chloride, and combinations ofthese materials, such as laminates of multiple layers of thesematerials, as well laminates of such materials further including paper.The plastic sheet material may be selected to be free of latex and otherallergenic materials.

The plastic sheet can have a fibre texture at an outer surface 18 of theouter pack 12 to configure the outer pack 12 for placement in directcontact with skin of the portion of the body. The fibre texture providesan amount of thermal insulation to disperse the cooling effect of thecold pack 10 and prevent the skin for becoming too cold. The fibretexture can reduce or eliminate the need to use a wrap or towel aroundthe cold pack, and therefore reduce the time it takes to apply the coldpack, which can be important in emergency situations. The cold pack 10can be used against clothes as well, and the fibre texture does notlimit potential modes of application of the cold pack 10.

The plastic sheet can have the fibre texture on one side 20 and bareplastic on the other side 22. The envelope 14 is formed with the fibretexture on the outside surface 18 and the bare plastic on opposite,inside surfaces, at 22, which undergo the heat-sealing.

The fibre texture can be formed by filaments or fibers that are integralto the plastic sheet and made of the same material as the plastic sheet.Alternatively, the fibre texture can be formed separate from the plasticsheet, such as a fabric weave, paper, or similar, that is then joined tothe plastic sheet, by adhesive, heat-sealing, etc.

With reference to FIG. 2, the outer pack 12 contains an amount ofphosphate ammonium nitrate 24. The amount of phosphate ammonium nitrate24 does not include a substantial amount of pure ammonium nitrate. Asubstantial amount of pure ammonium nitrate can be defined as, forexample, an amount that is required by regulation to be indicated on alabel of the cold pack 10. Another example of a substantial amount ofpure ammonium nitrate is an amount that can be removed from the coldpack 10 using only basic tools and used for another purpose. Becausepure ammonium nitrate is relatively volatile, can be explosive undercertain conditions, and is regulated in many jurisdictions, it can beadvantageous to omit such material from the cold pack. In someembodiments, small or trace amounts of pure ammonium nitrate can bepresent. In other embodiments, no ammonium nitrate is present in thecold pack 10.

In some embodiments, the phosphate ammonium nitrate 24 is provided inthe form of a prill.

Also disposed inside the outer pack 12 is a water-tight frangiblecontainer 26, which can include a heat-sealed plastic bag, and glassampoule, or the like. The frangible container 26 contains water 28 andis configured to rupture and release the water 28 into the inside of theouter pack 12 in response to an external force applied to the outer pack12. When the water is released and mixes with the amount of phosphateammonium nitrate 24, an endothermic reaction takes place, therebyfulfilling the function of the disposable cold pack 10.

In some embodiments, the water-tight frangible container 26 is a plasticbag that is shaped and sized to rupture when the outer pack 12 is foldedover itself about substantially any folding axis. To achieve this, thewater-tight frangible container 26 can be rectangular in shape and sizedto cover about more than half of the area within the outer pack 12, asmeasured parallel to the plastic sheet forming the envelope 14 of theouter pack 12.

It is advantageous that phosphate ammonium nitrate is highly soluble inwater and non-toxic. The specific composition of the phosphate ammoniumnitrate prill and the relative proportion of phosphate ammonium nitrateto water can be selected to tailor the cooling effect for the specificapplication of the cold pack and the material used for the outer pack,so that sufficient, but not too much, cooling is provided. Further, therelative proportion of phosphate ammonium nitrate to water can beselected to take into account the expected initial starting temperatureof the cold pack, just prior to activation.

The relative proportion of the phosphate ammonium nitrate to the watercan be selected to provide a target cooling effect to the portion of thebody to which the cold pack 10 is applied. The relative proportion canbe about 50% phosphate ammonium nitrate to about 50% water, by weight.

In some embodiments, the relative proportion is selected to be suitablefor general use of the cold pack, particularly when the fibre texture isprovided to the outside surface 18.

In some embodiments, the outer pack 12 is sized and shaped to fit afemale perineum, and the relative proportion is about 50% phosphateammonium nitrate to about 50% water, by weight. Such proportions can besuitable when the fibre texture is provided to the outside surface 18.Furthermore, such proportions can prevent the cold pack from becomingtoo cool and causing cold injury during postpartum application, whilesimultaneously reducing or eliminating the need to wrap the cold pack ina towel or other temperature buffer.

FIG. 3 shows a disposable cold pack 30 having a strap. The cold pack 30is similar to the cold pack 10. Like reference numerals designate likeelements, and the description for the cold pack 10 can be referenced.

The cold pack 30 includes a strap 32 having a fixed end 34 heat-bondedbetween overlapping portions of the plastic sheet, which form theenvelope 14, at one of the heat-sealed seams 35. The strap 32 can bemade of a material such as gauze, can be permeable to air, and can havesome elastic stretch. The strap 32 has a length selected to wrap aroundthe portion of the body and over the outer pack 12, so as to secure thecold pack 30 to the area of the body in need of cooling. The strap 32includes a fastener 36 at a free end 38 opposite the fixed end 34. Thefastener 36 is configured to engage the material of the strap 32. Thefastener 36 can include a hook side of a hook-and-loop fastener (e.g.,Velcro™).

Further embodiments and implementation details of thermotherapeutic padscan be found in US patent application publication 2012/0004713, which isincorporated herein by reference.

FIG. 4 illustrates a method 400 of manufacturing a disposable cold pack,such as the cold pack 10 discussed above. Like reference numeralsdesignate like elements, and the description for the cold pack 10 can bereferenced. However, it is to be understood that method 400 can bevaried, and need not work exactly as discussed herein in conjunctionwith each other, and that such variations are within the scope ofpresent implementations. For example, method 400 need not be performedin the exact sequence as shown, unless otherwise indicated.

Equipment such as a rotary band sealer, an impulse sealer, a verticalform fill sealing machine, a horizontal form fill sealing machine, andsimilar may be used to carry out one, several, or all of the stepsdescribed.

At 405, one or more pieces of a plastic sheet are provided. The piecesof plastic sheet can be cut from stock sheet to a suitable size andshape. In some embodiments, the plastic sheet is cut from stock to havea size and shape that provides an outer pack with a size and shapeselected to fit a typical female perineum region.

Next, at 410, the plastic sheet is heat-sealed to provide heat-sealedseams (such as heat-sealed seams 16 shown in FIG. 1) to three edges andform a water-tight envelope (such as envelope 14 shown in FIG. 1) havingan open top (such as open top 42 shown in FIG. 1). In other embodiments,as shown in FIG. 6, two opposite side seams 52 are heat-sealed for alength of plastic sheet that is longer than the envelope 14, and theside-sealed plastic sheet is subsequently cut to length, at 54, beforeor after the bottom seam 56 is heat-sealed. This can advantageouslyallow use of the same roll of stock sheet to form cold packs of variousdifferent lengths.

Further, at 415, a predetermined amount of phosphate ammonium nitrate isloaded into the envelope through the open top. A hopper can be used toload the phosphate ammonium nitrate. The hopper can be configured todispense the predetermined amount of phosphate ammonium nitrate.

Then, at 420, a water-tight frangible container (such as water-tightfrangible container 26 shown in FIG. 2) is loaded into the envelopethrough the open top. The water-tight frangible container contains apredetermined amount of water. The water-tight frangible container canbe formed by loading an open end of a plastic bag with the predeterminedamount of water and then heat-sealing the open end of the plastic bag.The same heat-sealing equipment can be used for the water-tightfrangible container and the envelope seams.

The order in which the phosphate ammonium nitrate and the water-tightfrangible container are loaded can be varied, and it may be easier, orprovide for faster manufacture, to load the water-tight frangiblecontainer after loading the phosphate ammonium nitrate.

The relative proportion of the predetermined amount of phosphateammonium nitrate to the predetermined amount of water in the water-tightfrangible container are selected to provide a target cooling effect.Example proportions are discussed elsewhere herein.

Lastly, at 425, the open top of the envelope is heat-sealed, at seam 16for example, to form a water-tight outer pack (such as water-tight outerpack shown in FIG. 1) and complete manufacture of the disposable coldpack 10.

Method 400 can alternatively include steps to manufacture a disposablecold pack having a strap, such as the cold pack 30 discussed above andshown in FIGS. 5 and 7. Like reference numerals designate like elements,and the description for the cold packs 10, 30 can be referenced.

At 430, an end 34 of a strap 32 is inserted into the open top 42 of theenvelope 14. This can be performed after the envelope 14 is filled withthe water container 26, and the phosphate ammonium nitrate (i.e., after420).

Then, at 435, the open top 42 of the envelope is heat-sealed, at seam35, to affix the strap 32 to the outer pack 12 and provide a water-tightseal to the outer pack 12 to complete the instant cold pack 30 (i.e.,instead of 425).

The heat-sealed seam 35 can be a single seam, such that the heat-sealingaction at 435 simultaneously affixes the strap 32 to the envelope 14 andseals the envelope 14 to form the water-tight outer pack 12 (see FIG.7). This can advantageously reduce the time required to manufacture thecold pack 30.

Alternatively, as shown in FIG. 5, the heat-sealed seam 35 can be acomposite seam that includes two separate heat-sealed seams 48 and 50.The inner heat-sealed seam 48 does not affix the strap 32 to theenvelope 14, and serves to provide a water-tight seal to the outer pack12. In some embodiments, the seams 48, 50 are made at about the sametime and the end 34 of the strap 32 can be prevented from being insertedtoo far into the envelope 14, so as to allow forming of the innerheat-sealed seam 48 without interference from the strap 32. In otherembodiments, the strap is affixed at seam 50 at the top or bottom of theenvelope 14 after all sealing seams, such as seam 48, have been made.This can be accomplished by leaving an unsealed outside margin ofplastic sheet material when making the water-tight seal. The outerheat-sealed seam 50 affixes the strap 32 to the envelope 14 and is notrelied upon to provide water-tightness. Use of this composite seam canadvantageously prevent rupture of the outer pack 12 due to stresses onthe strap 32, and help to ensure water-tightness of the outer pack 12.The same heat-sealing equipment can be used for the two seams 48, 50.

In another embodiment, as shown in FIG. 7, the strap 32 is attached tothe bottom end 58 of the envelope 14 before or after the envelope 14 isfilled with the water container 26 and the phosphate ammonium nitrate atthe top 42. A single heat-sealed seam or a composite heat-sealed seamcan be used to attach the strap 32. In some embodiments, the strap 32 isattached at a seam 50 to the bottom of the envelope 14 after theenvelope 14 is sealed completely closed, as this can allow for fastermanufacture.

FIG. 8 shows a cold pack 60 according to another embodiment. Likereference numerals designate like elements, and the description for thecold packs 10, 30 can be referenced.

The cold pack 60 is made with an envelope 62 cut from plastic sheetstock to provide for an outer pack 64 with a size and shape selected tofit a female perineum. With reference to FIG. 6, it should be noted thatthe envelopes 62 and 14 can be selected to have the same width andtherefore can be cut from the same length of side-sealed plastic sheetmaterial. For further understanding of the features and aspects of thecold pack 60, the description of the cold pack 10 can be referenced.

It can be seen from the above, that the present invention provides adisposable cold pack that is readily manufacturable in large quantitiesand convenient and safe to use in various clinical situations.

While the foregoing provides certain non-limiting example embodiments,it should be understood that combinations, subsets, and variations ofthe foregoing are contemplated. The monopoly sought is defined by theclaims.

What is claimed is:
 1. A method of manufacturing a disposable cold packfor cold therapy, the method comprising: heat-sealing plastic sheet toform a water-tight envelope having an open top; loading a predeterminedamount of phosphate ammonium nitrate into the envelope through the opentop; loading a water-tight frangible container into the envelope throughthe open top, the water-tight frangible container containing apredetermined amount of water, a relative proportion of thepredetermined amount of phosphate ammonium nitrate to the predeterminedamount of water selected to provide a target cooling effect to a portionof a body to which cooling is applied; and heat-sealing the open top ofthe envelope to form a water-tight outer pack.
 2. The method of claim 1,wherein the plastic sheet has a fibre texture on one side and bareplastic on an opposite side, and the envelope is formed with the fibretexture on an outside surface and the bare plastic on an inside surfacethat undergoes the heat-sealing.
 3. The method of claim 1, wherein therelative proportion is about 50% phosphate ammonium nitrate to about 50%water, by weight.
 4. The method of claim 1, further comprising:inserting an end of a strap between plastic sheet of the envelope afterthe open top of the envelope has been heat-sealed, the strap having afastener at a free end opposite the inserted end; and heat-bonding thestrap to the envelope.
 5. The method of claim 1, further comprisinginserting an end of a strap into the open top of the envelope, the straphaving a fastener at a free end opposite the inserted end, whereinheat-sealing the open top of the envelope affixes the strap to the outerpack and provides a water-tight seal to the outer pack.
 6. The method ofclaim 1, further comprising forming the water-tight frangible containerby loading an open end of a plastic bag with the predetermined amount ofwater and heat-sealing the open end of the plastic bag.
 7. A disposablecold pack for providing cold therapy to a portion of a body, the coldpack comprising: an outer pack formed of a water-tight sealed envelope,the outer pack having an outer surface configured for placement on skinor clothing covering the portion of the body; an amount of phosphateammonium nitrate contained inside the outer pack; and a water-tightfrangible container disposed inside the outer pack, the water-tightfrangible container containing water, the water-tight frangiblecontainer configured to release the water into the inside of the outerpack in response to an external force applied to the outer pack; arelative proportion of the phosphate ammonium nitrate to the waterselected to provide a target cooling effect to the portion of the body.8. The disposable cold pack of claim 7, wherein the water-tight sealedenvelope is made of plastic sheet having a fibre texture at the outersurface of the outer pack.
 9. The disposable cold pack of claim 7,wherein the relative proportion is about 50% phosphate ammonium nitrateand about 50% water, by weight.
 10. The disposable cold pack of claim 7,wherein the water-tight sealed envelope is formed of at least one layerof plastic sheet that is heat-sealed at one or more heat-sealed seams.11. The disposable cold pack of claim 10, further comprising a straphaving a fixed end heat-bonded between overlapping portions of theplastic sheet, the strap having a length selected to wrap around theportion of the portion of the body and over the outer pack, the straphaving a fastener at a free end opposite the fixed end, the fastenerconfigured to engage a material of the strap.
 12. The disposable coldpack of claim 7, wherein the water-tight frangible container comprises aheat-sealed plastic bag.
 13. A disposable cold pack for providing coldtherapy to a portion of a body, the cold pack comprising: an outer packformed of a water-tight sealed envelope formed of at least one layer ofplastic sheet that is heat-sealed at one or more heat-sealed seams, theplastic sheet having a fibre texture at an outer surface of the outerpack to configure the outer pack for placement in direct contact withskin of the portion of the body; an amount of phosphate ammonium nitratecontained inside the outer pack; and a water-tight frangible containerdisposed inside the outer pack, the water-tight frangible containerincluding a heat-sealed plastic bag containing water, the water-tightfrangible container configured to rupture and release the water into theinside of the outer pack in response to an external force applied to theouter pack; a relative proportion of the phosphate ammonium nitrate tothe water selected to provide a target cooling effect to the portion ofthe body, the relative proportion being about 50% phosphate ammoniumnitrate to about 50% water, by weight.
 14. The disposable cold pack ofclaim 13, further comprising a strap having a fixed end heat-bondedbetween overlapping portions of the plastic sheet, the strap having alength selected to wrap around the portion of the body and over theouter pack, the strap having a fastener at a free end opposite the fixedend, the fastener configured to engage a material of the strap.